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Bio 152 > Evolution > Flashcards

Evolution Flashcards

0
Q

The two components of scientific theory

A
  1. Pattern component: a statement that summarizes a series of observations about the natural world. Facts - about how thins are
  2. Process component: is a mechanism that produces that pattern or set of observations
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1
Q

Special Creation

A
  1. All species are independent, in the sense of being unrelated to each other.
  2. Life on Earth is young - just 6000years old
  3. Species are immutable, or incapable of change
  4. Created by a supernatural being
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2
Q

Typological thinking

A

Based on the idea that species are unchanging types and that variations within species are unimportant or even misleading - Christians

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3
Q

Aristotle’s Great Chain of Being

A

An ordered linear scheme of organisms

  1. Species are fixed types
  2. Some species are higher - in sense of complexity (better)

Humans on top

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4
Q

Lamarck’s Theory of Evolution

A

Based on the great chain of being, however, species were not fixed. Species evolved - climbing up the ladder

  1. Species not fixed but evolve
  2. Simple organisms originate at the base of the chain by spontaneous generation
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5
Q

Population thinking

A

The idea that instead of being unimportant or an illusion, variation among individuals in a population was the key to understanding the nature of species

Individuals with certain traits leave more offsprings than others do

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6
Q

Predictions of the theory of evolution by natural selection

A
  1. Species change through time

2. Species are related by common ancestry

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8
Q

Evidence for change

A
  1. Fossils
  2. Sedimentary rocks - help determine timing
  3. Vestigial traits - reduced or incompletely developed structure that has no function, or reduced function but similar to other related species. (tail bones in humans)
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9
Q

Transitional feature

A

Is a trait in a fossil that is intermediate between those of ancestral and derived (younger) species.

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10
Q

Current examples of change in time (rapid change)

A
  • bacteria evolved resistance to drugs
  • insects evolved resistance to pesticides
  • weeds evolved resistance to herbicides
  • change in bird migration (eg. Blackcap migration to UK/Spain form Germany).
  • domesticated animals (dog breeds)
  • crops (seedless bananas)
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11
Q

Phylogenetic tree

A

A branching diagram that describes ancestor-descendent relationships among species or other taxa

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12
Q

Homology

A

The similarities between species because they inherited the trait from a common ancestor

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13
Q

Genetic homolgy

A

Occurs in DNA nucleotide sequences, RNA sequences, or amino acids sequences

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14
Q

Development Homology

A

Is recognized in embryos

  • tails
  • gill pouches

Lose them when we’re done

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15
Q

Structural Homology

A

Similarities in adult morphology (form)

The number of bones in a human arm is the same as the that of a birds wing, a seals arm, a horses leg, and a turtles wing.
The structure is similar but obviously different

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16
Q

Internal consistency

A

The observation that data from independent sources agree in supporting the predictions made by a theory

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17
Q

Darwin’s four postulate

A
  1. The individual organisms that make up a population vary in traits they possess, such as their size and shape
  2. Some the trait differences are heritable, meaning that they are passed on to offspring. For example tall parents tend to have tall offsprings
  3. In each generation, many more offspring are produced than can survive. Thus, only some individuals can survive long enough to reproduce offsprings
  4. The subset of individuals that survive best and produce the most offsprings is not a random sample of population. Instead, individuals with certain heritable traits are more likely to survive and reproduce. Natural selection occurs as a result (the individuals are are selected naturally, by the environment)
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18
Q

Fitness

A

The ability to produce surviving, fertile offspring relative to that ability in other individuals of the same population

19
Q

Adaption

A

Is a heritable trait that increases the fitness of an individual in a particular environment relative to individuals lacking the trait.

Adaption increases fitness

20
Q

Selection

A

Differential reproduction as a result of heritable variation - not a purposeful choice

21
Q

Case Study 1: how did Mycobacterium tuberculosis become resistant to antibiotics?

A
  1. By chance some of the M. TB had a mutation on the rpoB gene that changed a C to a T.
  2. This caused the drug (rifampin) to become inefficient at binding to the RNA polymerase.
  3. Cells with T mutation continued to increase in numbers after therapy ended
  4. Drug-resistant M. TB now dominated the population, so the second round of rifampin therapy was futile
22
Q

Testing Darwin’s postulate through case study 1

A
  1. Did variation exist in the population? yes - resistant and non-resistant M. Tuberculosis were present.
  2. Was the variation heritable? Yes - drug resistance was passed on to the daughter cells.
  3. Was there variation in reproductive success? Yes - only a tiny fraction of M TB survived the first round of antibiotics to reproduce.
  4. Did selection occur? Yes - when rifampin was present, certain cells - those with the drug-resistant allele - had higher reproductive rates.
23
Q

Common misconceptions: “evolutionary change occurs in organisms”

A

Correction:

  1. Natural selection just sorts existing variants in organisms; it does not change them
  2. Evolutionary changes occurs only in populations
  3. Acclimatization (changes in an individual phenotype that occurs as a response to changes in environment) does not equal adaptation. No alleles have changed. (eg. Tanning)
24
Q

Common misconceptions: “adaptations occur because organisms want or need them.

A

Correction:

  1. Mutation, the source of new alleles, occurs by chance.
  2. Evolution is not goal directed or progressive.
  3. There is no such thing as higher or lower organisms.
25
Q

Common misconceptions: “organisms sacrifice themselves for the good of the species”

A

Correction:
1. Individuals with alleles that cause self-sacrificing behavior die and do not produce offspring, so these alleles are eliminated from the population.

26
Q

Common misconceptions: “evolution perfects organisms”

A

Correction:

  1. Some traits are nonadaptive
  2. Some traits cannot be optimized due to fitness trade-offs
  3. Some traits are limited by genetic or historical constraints.
27
Q

Importance of Darwin’s and Wallace’s theory of evolution by natural selection

A

Introduced new ideas:

  1. Species are not static and unchanging but instead evolving
  2. Replaced typological thinking with population thinking
  3. It was scientific - it proposed a mechanism that could account for change through time and made predictions that could be tested through observation and experimentation
28
Q

Evolution by Natural selection

A

If certain alleles are associated with the favored phenotypes, they increase in frequency while other alleles decrease in frequency. The result is evolution

29
Q

genetic variation

A

The number and relative frequency of alleles that are present in a particular population

30
Q

What are the four ways in which selection affect genetic variation

A
  1. Direction selection
  2. Stabilizing selection
  3. Disruptive selection
  4. Balancing selection
31
Q

Direction selection

A

-Changes the average value of a trait
-Tends to reduce genetic diversity
-Tends to increase frequency of advantageous alleles
-Decrease frequency of disadvantageous alleles (purifying selection).
Eg cliff swallow popualtions average body sized increased in 1966 (a cold and rainy year)

32
Q

Stabilizing selection

A

Reduces variation in a trait

  • Tends to stabilize traits to an intermediate level, decreases variation in extreme traits
  • No change in average value of a trait over time

Eg. Birthweight - high mortality rate for small babies and very large babies. Low mortality rate amongst babies that weigh 7pounds (avg)

33
Q

Disruptive selection

A
  • Increases variation in a trait
  • complete opposite of stabilizing selection
  • favors extreme phenotypes at both ends
34
Q

Balancing selection

A
  • Maintains variation in a trait

- No single phenotype is favored in all populations of a species at all times

35
Q

Genetic drift

A

Defined as any change in allele frequencies in a population that is due to chance

36
Q

Sampling error

A

Occurs when the allele frequencies of a chosen subset of a population are different from those in the total population

37
Q

What population size is most affected by genetic drift?

A

Small populations, but occurs in all population, in every generation

38
Q

Founder effect

A

A change in allele frequencies that occurs when a new population is established

39
Q

Genetic bottleneck

A

Is a sudden reduction in the number of alleles in a population.
Drift occurs during genetic bottlenecks and causes a change in allele frequency

40
Q

Gene flow

A
  • When an individual leaves one population, nouns another, and breeds.
  • The movement of alleles between populations
  • Usually equalizes allele frequencies between both populations
  • is random in with respect to fitness (the arrival or departure of alleles can increase or decrease average fitness, depending on the situation)
41
Q

Mutation

A

Mutation is the source of all genetic variation

42
Q

Point mutations

A

If a change in nucleotide sequence occurs in a stretch of DNA that codes for protein, the new allele may result in a new amino acid sequence
- if occurs in DNA the new allele may result in a change in regulation of the expression of other alleles.

43
Q

Chromosome-level mutation

A

Causes gene duplication

-if duplicated genes diversify via point mutations, they can lose their function or create new alleles

44
Q

Lateral gene transfer (mutation)

A

Transfer of genetic information from species to the next
-might be a more important source of genetic variation then previously realized.

Eg. Virus genes in human genome

Bio 152 (7 decks)

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